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Abstract  

Extraction of As(III) and As(V) from sulphuric acids solutions of H2SO4 of various concentration (50–200 g/dm3 with Cyanex 923 dissolved in Exxsol 220/230 (50% v/v) was studied and compared. Cyanex 923 can be considered as an effective arsenic extractant. Sulphuric acid is co-extracted. Extraction both of As(III) and As(V) occurs quickly and the equilibrium is obtained after 5 minutes. The isotherms of As(III) and As(V) extraction at various sulphuric acid concentrations were determined and used to model the multistage countercurrent process. Arsenic can be stripped with water.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
Xue Shuyun
,
Yang Yonghui
,
Yang Yanzhao
,
Sun Sixiu
, and
Bao Borong

Abstract  

A study on solvent extraction of sulfuric acid by tri-octylphosphine oxide (TOPO) in n-heptane has been made. Extraction coefficients of H2SO4 as a function of H2SO4 concentration in aqueous phase, and extractant concentrations in organic phase have been studied. The composition of extracted species, equilibrium constants of extraction reaction have been evaluated. These results are important for interpreting extraction equilibrium data of uranium(VI) or other metal ions with TOPO in sulfuric acid media.

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dioxide production using sulphuric acid technology, and one of the first stages of the production is the reaction of the titanium raw material with the sulphuric acid. Elemental and phase compositions of ilmenite have an influence on the way of processing

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Abstract  

The extraction of sulphuric acid from solutions containing hydroxylamine sulphate and ammonium sulphate with Cyanex 923 and the acid stripping from loaded Cyanex 923 are studied at 20 and 50°C. The effect of the numbers of extraction and stripping stages and the volume phase ratios in extraction and stripping upon sulphuric acid recovery is discussed. The process can be design to obtain a high or low recovery of sulphuric acid but with its low or high concentration, respectively.

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Abstract  

The reaction of ilmenite titanium raw material with sulphuric acid was investigated in ‘hazard’ type calorimetric system. The investigations show the essential influence of initial temperature, particle size distribution and concentration of sulphuric acid on rate and heat power of reaction and determine the limits of safety of the process and also its efficiency.

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Abstract  

The kinetic of the reaction ilmenite with sulphuric acid was studied using non-adiabatic and non-isothermic calorimetric device system. The kinetic model based on interphase surface and kinetic models found in literature which are usually applied were tested. The best agreement between experimental and calculated values was found with model based on first order of reaction and model of contracting volume.

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Abstract  

The extraction of uranium(VI) from sulfuric acid medium with tri-octylphosphine oxide (TOPO) in n-heptane was studied. Accompanied with the increase in the concentration of H2SO4, the distribution coefficient of uranium(VI) increased in the region of dilute sulfuric acid. When the concentration of H2SO4 surpassed 3.5 mol·dm−3, the distribution coefficient of uranium(VI) was at maximum. This result was due to the competition extraction between uranium(VI) and H2SO4. From the data, the composition of extracted species and the equilibrium constant of extraction reaction have been evaluated, which were (TOPOH)2UO2(SO4)2 (TOPO) and 107.6±0.15, respectively.

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The process of thermal degradation of lignins of hard wood (birch, aspen, oak), obtained under the wood treatment with 66% sulphuric acid in the form of acid-in-soluble and soluble fractions, has been investigated by thermal methods. Activation energy values of lignin pyrolysis have been determined at the stage of increasing rate of weight loss. It has been established that the difference in their thermal properties is conditioned by the structural changes in the process of isolation from wood. It has been suggested that acid-soluble lignins have a higher density than acid-insoluble ones. Sulphuric acid lignins of birch, in particular acid-soluble lignin, are assumed to possess a more homogeneous structure than sulphuric acid lignins of other species

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Abstract  

The extraction of plutonium(VI) and plutonium(III) from sulphuric acid by TOA in toluene has been studied as a function of the acid and tri-octyl amine concentration. A comparison of the extraction properties of plutonium with those of uranium(VI) and uranium(IV) has been made. It was found that the extraction properties of plutonium(VI) are very similar to those of uranium(VI) and that TOA is a relatively poor extractant for plutonium(III). Uranium(IV) shows better extraction properties than plutonium(III). The results obtained are considered in the light of the stabilities of the complexes formed by these elements in the organic and aqueous phase. A method of separation of both elements by solvent extraction based on changing their oxidation states is suggested.

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Abstract  

The reaction of sulphuric acid with titanium raw materials runs violently with simultaneous emission of gases. Such run of reaction creates danger of explosion. This process is very complicated from the reason of complexity of reactions and variety of compounds in reaction mixture. To determine safe conditions of reaction with high efficiency, it is necessary to investigate phase composition products of reaction. Products of reaction were investigated by using X-ray diffraction. However reaction products show high amorphy and this is the reason of difficulties to determine all phases. For this reason also was used additional method — ‘drop’ calorimeter. This method is used for determination of average specific heat of liquid or solid samples. In this case, this method was used for verification of phase composition of products of reaction. On the basis of investigation the phase composition of reaction product is following: titanyl sulfate, iron(III) sulfate, monohydrated iron(II) sulfate, magnesium sulfate and unreacted remainders of ilmenite and magnesium silicate.

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